The present invention relates to a method and a device for dehydrating a heavy oil, for example, a method applicable to dehydrating operation in a orimulsion burning device.
Technology for dehydrating heavy oils includes (i) methods in which reagents are added, (ii) methods in which liquids are separated by means of heat diffusion, and (iii) methods in which liquids are separated by means of electricity. A large number of the methods in which reagents are added as designated in (i) above have been disclosed in patent applications including that filed by NIKKO ENGINEERING (JP-A-53-111649) which is targeted to an oil-containing waste water, i.e., a system containing a minimum amount of oils in a large volume of water. In this publication, a method is disclosed in which an acid and an emulsion destroyer are added to a waste water to effect emulsion break, followed by neutralization, aggregation and floating/separating processes, whereby facilitating removal of oil components in a COD-rich waste water, SS and surfactants. The emulsion destroyer used herein is otherwise referred to as an emulsion breaker, which is a chemical serving to break the interface of the emulsion and to promote aggregation and integration of dispersed particles, thus being a kind of surfactants.
In a method for desalting a crude oil disclosed by HAKUTO NARCO CHEMICAL (JP-A-59-152991), a water-in-oil (W/O) emulsion breaker and an oil-in-water (O/W) emulsion breaker are added to a feed crude oil and to a washing water, respectively, whereby reducing the oil content in the waste water while improving the desalting rate and dehydrating rate of the crude oil. However, this method is not advantageous economically since it requires the emulsion breakers in large amounts to raise the dehydrating rate. In addition, it involves disadvantage of a prolonged residential time during two-phase separation effected by the emulsion breakers, which results in slow production as well as necessity of a huge two-phase separation tank while allowing for only a limited amount of dehydration even with a large amount of the emulsion breakers.
In the methods designated by (ii) above in which liquids are separated by means of heat diffusion it is very difficult to effect oil/water separation exclusively by means of the heat although some auxiliary effect can be achieved.
In the methods designated by (iii) above in which liquids are separated by means of electricity, application of a high voltage to an orimulsion containing 30% water results in a current through the water to create a overcurrent state, showing almost no dehydrating effect.
One of the heavy crude oils, orinocotar produced in Venezuela, is an extremely heavy, highly viscose and not suitable to be transported. Accordingly, it is transported after dispersing the water by a dispersant to convert to an emulsion (hereinafter referred to as orimulsion), and then used as, for example, a fuel. However, burning of the orimulsion containing 30% water as it involves disadvantage of heat loss during burning as well as reduced desulfurization performance during subsequent removal of sulfur oxides contained in gases by flue-gas desulfurization. Nevertheless, by burning the orimulsion containing 30% water after dehydrating to the water content of 1% by weight, the heat loss during the burning can be reduced by 2.7%, the water content in a boiler waste gas is reduced each by 4%, the waste gas temperature in the flue-gas desulfurization device is lowered by 5.degree. C., whereby achieving the advantage of 2% increase in desulfurization performance. Based on such findings, the present invention has been established.